The present invention relates as indicated to a flank drive for planing hull and displacement craft, which drive includes a wheel body mounted in the craft or boat for driven rotation about a vertical axis. A plurality of propeller housings are rotatably disposed within the wheel body. The propeller blades are adjustable and move through the water in sinuating lines at each revolution of the wheel body. As a result, the propeller blades exert mainly flank forces, that is, forces transverse to the direction of the boat, to the surrounding water.
Screws are well known as a means for propelling planing hull craft and high speed displacement crafts, but have proved disadvantageous due to their decreasing efficiency at high boat speeds and the high propeller r.p.m. incident thereto.
The buoyancy principal of ship screws as well as that of conventional vane-screw propellers having a high circumferential speed in relation to the boat speed results in a high unit load on each propeller blade, and in heavy turbulent water, this results in a considerable loss of propulsion. This is in marked contrast with the present invention which employs a flank drive wherein more water is seized athwartships with increasing boat speed thereby resulting in a low acceleration of the water.